Apparatus for measuring the torsional shear strength of soil



July 22, 1952 l.. o. T. cARLsoN APPARATUS FOR MEASURING THE TORSIONAL sHEAR STRENGTH oF son Filed March 6, 1948 INVENToR LVMAN OTTO THEODOKE ARLSoN /fTroR/vfy Patented July 22, 1952 Join. .iA

of the ground is generally "performed '-by'obtaining samplesjofthe,groundand byexarniningthe same in thejlaboratory; HT liis'rn-armer of proce d? ing, however, is rather' tediou'sand expensive and is impaired. bythe' dravvback'thfat vthe samples often are damaged during the" lifting from 'the ground and jalsoma'ybe during the .transport to, the laboratoryall of whichof course 'Im'ay cause that the 'results-'of the' examination point 'There are;l however, other ".m'etho'ds forfde'terfmining the shear strength ofthe ground directly on' 'the eldfthat" isV to say, 'th'eso called' probing methods. When performing these latter methods,

' the inventi'onhas for its object the performance 'Hitherto'the investigation of theshe'a'r strength .1n-411 in Fig. 1, 'andy j j--Fig 4 a-v transversal section along- 'i :i`1e v jl'ne protecting device. 'The shearfstrength' [ofv they ground is thereupon calculated the torsionalmoment. l

The improvements inthe method'fas' well-j as meansjfor performing thesame are hereinafter nearer'v described withv 'reference to the a c` ompanying; drawing, wherein ;y

" Fig: 1 shovvsjs'chematicallyby;Way of example an embodimentjdf'a device forthe investigation of groundinvertical sect-ion; f i Fig. 2 a' gtop`vi' evv{ofthe device,

lFig; 3 'laf'transversal sectin along the/line IV-1Vin'r'ig.- 1. ff According to the invention, the lowerrnostportioneof the device-,the auger body, consistsofa a body of 'any shape is driven downinto the ground Y and pulled out ofit, "andf'the necessary force is measured. Yet, these methods'V are im-` paired by-'the drawback that the 'shear strength of the ground can not be determined directly. from the .measured force, and on this account it isnec-l essarin' order t'obtain the correct valueoffthe shear'stregm to gangers@ employed mea 'by another reliable' niethodl 'Asglalt .presents .la method 'seems not" 'to be" available-laboratry areA performed on sampleswhich may hai/erheen tests, which in .and :per s'enay be' rather exact,

damaged during the extractionof thesame; or

during the transport-consequently also the probing methods leave unreliable results.

The method according to the present; invention is very easily performed and renders pos- I sible to make a direct calculation of the shear strength of the ground. No gauging is therefore necessary. The test is made directly in the ground so that no damages are caused in the ground due to taking samples. The improvements in performing investigations of ground as per the invention are substantially characterized by the feature, that an auger body is driven into the ground and then rotated, whereupon the `required torsional moment is measured, the auger body being shaped thus that, when being driven into the ground, as little stirring of the earth as possible is caused, the auger body during the rodll with 'circular cross section andprovided with* aile-number' of yWings 2, for .instance,-' four Wings -ofma'i-nly rectangular shape; #Both therod I- andth'e wings 2-have as little diameter"`and thickness espectivelya's possible lrelation-"to the ystrength vso 'as'*-to' avoid,`as -f'ar as possible; any stirring'fof. the 'earth whe'n the auger iis driven into? the ground. The* auger rod `I 'f' has furthermore Asuch'a length that fthe-protecting' tube 4 surrounding the-'extension ofthe auger rod I does Vnot stir th'e'l-earth to b'e tested; when the protecting vtube-*fis -driven 'down intofthe ground. J' f" Ihe extension5 350i the VaugerrodI consists of lengths* of; J for V1instance-,---on'e `yard, and equally the protecting tube is composedeo-flengths of' one yard.-L lOnthev lowermostend cf the protecting tube there is provided a guiding device 5, through which the auger rod I passes with good tting. The diiferent lengths of the protecting tube are assembled by means of bushings E. Certain of those are provided with guiding devices'I for the extension rods 3. 0n the uppermost end of the rod 3 there is provided a swing-bar 8, and the protecting rod 4 is on its upper end provided with a special fitting 9 on which is mounted a disk I0 with graduation. By means of a set screw I I the tting 9 may be firmly connected with the protecting tube 4. Internally the fitting 9 is provided with a guiding device I2 for the rod 3. Furthermore, the fitting 9 is provided with a swing-bar I3 which by means of spring-balances I 4 is connected with the swing-bar 8. When swinging the bar I3, the

torsional moment is thus by means of the springbalances I4 imparted to the swing-bar 8.` In

order to check the angle of torsion, an indicatory driven down into the ground, but during this tube, and in this position the device will be:4

operation the upper fitting `lwith the'di'sk Il l-.L

and the swing-bars I3 and 8 are-takenl olf. `fAsf soon as the -desired depth is reached, the said are mounted, whereupon the rod together with `the auger body is pressed down toaignositior-'lV777 shown in Fig. 1, in which the test is performed.' 'v

, stung 9, the disk lo and the swing-bars' Italia a tionoffthe shaft linside the tube, said operating The torsional moment may also be measuredv f.,

by other means than the above described. For instance, thermeasuring may be performed by means of electrical elongation meters placed directly onthe wings of the auger body. Obviously variousv changes might be made in the details ofv .1. AVA 1 tool for investigating ground comprising a shaft, an augeron the lower end Vofthe shaft having a plurality of wings` radiallyf extending therefrom a. Profiwin/e ibgsurtviifidn the major v`part of the shaft aboveV said auger. said shaftl being rotatable and'axially slidable in said tube and having its upper endvprojectingffrom thetube, and operating. meanson said projecting upper end for rotating said shaft and said auger., said tube'being provided -atit s lower end with guide means for said shaft, said lower tubeend Y forming an abutment for, said wings tion` of the shaft inside 4the tube. f

2., VAgtool f orinvestigating ground comprising a shaft, `anauger on the lower endqof the shaft havingV aplurality of wings radially extending therefrOm. a protective tube surrounding the major part of the shaft abovesaid augensaid shaftbeing rotatable and axially slidable ingsaid tube and having its upper end projecting from the tube, and operating means on saidprojecting upper end for rotating said shaft and said auger, said operating means comprising a first handle xedly secured to saidshaftfa second handle rotatably mounted on the upper vrend of said tube, and spring means interconnecting said handles uponretracfor entrainment, of the first handle by the secondV handle.

.31 ,A tool accordingto claim 2 comprising'fafscale 4 member carried by the upper end of said tube and indicator means, cooperating with Vsaid scale member, carried by saidl rst handle.

'4. A tool for investigating ground comprisinga shaft, an auger on the lower end of the shaft having a plurality of Lwings radiallyextending therefromf, ag` protective .tube surrounding the major part of the shaft above said auger, said shaft being rotatable and axially slidable in said tube and having its upperend projecting from the'tubean'd operating means on said projecting It. `upperend*forfrotating said'shaft and said auger, said tubewbeing provided at its lower end with guide means for said shaft, said lower tube end forming an abutment for said wings upon retracmeans'4 comprising a first handle fixedly secured to said shaft, a second handle rotatably mounted on the upper end of said tube, and spring means interconnecting said handles for entrainrnent of the'irst handle by'the'second handle. 'I A tool for'investigating ground comprising a shaft, lanaug'e'r on the lowerend of the. shaft having a plurality of wings radially extending therefrom, a protective tube Vsurrounding the major part o f the shaft above said augerfsaid shaftbei'ng rotatable'and axially slidable in said tube -`and `having its upper end projecting from the tube, operating means on said projecting upperend. forrotating said shaft and said auger, said'tube'being provided at its lower end'with guide means forsaid shaft, said lower tube end forming anv abutment for said wings upon re-'f traction of the'shaftinside the tube, said operati#- ingr means 'comprising a first handle fixedlylse` 'cured to said shaft, a second handle Vrotatably mountedon the upper end of said tube, and spring` means interconnecting saidhan'dles for entrainnient of the rst handle by the second handle;v a scale member carried by the upper end'of said tube and indicatormeans, cooperatrlwith said scalemember, carried by; said rsthandle.`

o'rfro THEODORE CARLSQN;

"` REFERENCE-S CITED The following references areof record in the file of .this patent:

' UNITED STATES PATENTS Number' Namel Dare 722,576 vGrand Mar. 10. '190.3 1,574,491 Leake f.,.' Feb. 23 1926 r`2, 2! f5,' 466 1 yDames etal. Sept. 22, 1942 2331i2,919;l ,Demb K ;Au g. 21,1945

f FOREIGNIPATENTS Numberl Countryf Date Great Britain Oct. 19.1922 

